Alloyed cast steel and article made therefrom

ABSTRACT

Disclosed is structural low-alloy manganese cast steel having increased hardness and wear resistance, and an article made therefrom. In particular, after carrying out conventional bulk hardening followed by tempering, the disclosed steel has hardness of approximately 418 to 512 HB and is suitable for use in railway engineering, in particular for manufacturing parts of freight car trucks such as a friction wedge. Due to improved hardness and wear resistance of the parts made of the steel according to the present invention, an increase in inter-repair service life, in particular, of the friction wedge/friction plate friction pair is provided without a significant increase in cost for the parts.

FIELD OF THE INVENTION

The present invention relates to metallurgy, in particular to structuralalloyed cast steel suitable for use in railway engineering, inparticular in the railway car manufacturing industry.

BACKGROUND OF THE INVENTION

With the development of railway engineering, more and more attention isdevoted to the development of improved structural materials withincreased reliability and durability, which are at the same timerelatively inexpensive. Such materials find their use in construction ofabove ground railways and manufacturing of various parts of the railwayrolling stock. Further, the strictest requirements in terms of servicereliability are imposed on steel used for railway rails and parts offreight and passenger car trucks, particularly for parts requiringdurability and wear resistance, such as center plate discs, wheels andaxles of car trucks, friction wedges and friction plates.

A friction wedge for freight car trucks is a part of the shock absorberof the car providing stability and smoothness of movement duringoperation. Currently, there are many different variations of frictionwedges made of different materials. For example, friction wedges aremade of grey cast iron class 35 [Technical specifications3183-234-01124323-2007], class 25 [Bondarenko A. F., Gorenkov A. A.,Fedin V. M., Borts A. I., Hardening of friction wedge made of grey castiron by volume-surface hardening II Vestnik VNIIZhT, 2010, volume 3, pp.40-42.] as well as of 20 L grade steel [Gabets A. V., Developing thecomposition and technology for producing special modified cast iron withincreased operational durability for friction units of railway rollingstock: PhD thesis in Technical Sciences: 05.16.01.—Moscow, 2014.], 20GL,20FL, 20GTL grade steel [Bondarenko A. F., Gorenkov A. A., Fedin V. M.,Borts A. I., Steel friction wedge hardened by volume-surface hardeningII Vestnik VNIIZhT. 2010, volume 3, pp. 43-45. However, a generaldisadvantage of friction wedges made of said materials is insufficienthardness and wear resistance of the wedges for trucks with a load ofover 25 tf per axle.

Therefore, it is the object of the present invention to provide analternative structural material suitable for manufacturing frictionshock absorbers of friction force vibrations, the material havingincreased strength and durability while being relatively inexpensive.

SUMMARY OF THE INVENTION

In the present invention, the aforementioned problem is solved byproviding a new composition of alloyed cast steel characterized by thefollowing content of elements (wt. %):

Carbon (C) 0.27 to 0.35 Manganese (Mn) 1.20 to 1.40 Silicon (Si) 0.60 to0.80 Chromium (Cr) 0.10 to 0.25 Aluminium (Al) 0.02 to 0.05 Vanadium (V)0.015 to 0.040 Phosphorus (P) no more than 0.030 Sulfur (S) no more than0.030 Nickel (Ni) no more than 0.30 Copper (Cu) no more than 0.30Molybdenum (Mo) no more than 0.08 Iron (Fe) the remainderwherein the complex alloying coefficient CE for said steel calculated asCE=C+(Mn+Si)/6+(Cr+Mo+V)/5+(Ni+Cu)/15 is no less than 0.68% wt.

Thus, as a result of extensive research, the present inventorsdiscovered that steel with the above narrowed ranges of carbon andmanganese content, specified ranges of chromium, aluminium and vanadiumcontent, and stricter requirements for phosphorus, sulfur, copper andnickel content, and characterized by the specified value of thecalculated coefficient (i.e., the complex alloying coefficient CE)introduced by the inventors differs from the 30GSL grade steel selectedas the prior art for the present invention in significantly higherhardness and wear resistance even without the use of advanced hardeningmethods. In particular, higher hardness and wear resistance values wereachieved using conventional bulk hardening followed by tempering, andaccordingly, the manufacturing cost increase for such steel isinsignificant compared to prior art materials; in particular, said costincrease is 3-7% compared to that for 20GL grade steel, for example.

Thus, the technical effect of the invention is in providing increasedhardness and wear resistance of articles made of the steel according tothe invention without a significant increase in their manufacturingcosts. Another technical effect is in providing increased hardness andwear resistance of surfaces of a friction wedge of freight car trucksand increased inter-repair service life of a friction wedge/frictionplate friction pair. A further technical effect of the invention is inavoiding expensive processing methods for the disclosed steel andreplacing them with simple bulk hardening followed by tempering, whileproviding an increase in hardness and wear resistance values.

The present invention further provides an article made of the steelaccording to the invention. According to a particular embodiment, thearticle is a friction wedge for freight car trucks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows surface hardness of a part (a friction wedge made of steelaccording to the present invention) obtained after heat treatment (bulkhardening with tempering) as a function of the complex alloyingcoefficient CE of said steel calculated as

CE=C+(Mn+Si)/6+(Cr+Mo+V)/5+(Ni+Cu)/15.

DETAILED DESCRIPTION OF THE INVENTION

Comparative tests were carried out in order to determine hardness valuesfor samples made of the steel according to the present invention ascompared to the prior art materials used for manufacturing frictionwedges: grey cast iron class 25 and steel grade 20GL. The test resultsare shown in Table 1 below.

TABLE 1 Hardness, HB Steel according to the invention 418-512 Grey castiron class 25 197-260 Steel 20GL 140-180

Brinell hardness measurements for the samples were carried out inaccordance with the following procedure.

GOST 9012-59: Metals. Brinell method for measuring hardness.

1. Alloyed case steel characterized by the following content of elements(wt. %): Carbon (C) 0.27 to 0.35 Manganese (Mn) 1.20 to 1.40 Silicon(Si) 0.60 to 0.80 Chromium (Cr) 0.10 to 0.25 Aluminium (Al) 0.02 to 0.05Vanadium (V) 0.015 to 0.040 Phosphorus (P) no more than 0.030 Sulfur (S)no more than 0.030 Nickel (Ni) no more than 0.30 Copper (Cu) no morethan 0.30 Molybdenum (Mo) no more than 0.08 Iron (Fe) the remainder

wherein the complex alloying coefficient CE for said steel calculated asCE=C+(Mn+Si)/6+(Cr+Mo+V)/5+(Ni+Cu)/15 is no less than 0.68% wt. 2.Alloyed cast steel according to claim 1, characterized in that itshardness after bulk hardening followed by tempering ranges from 418 to512 HB.
 3. An article made of the steel according to claim 1 by casting.4. The article according to claim 3, characterized in that the articlemade of the alloyed cast steel is a friction wedge of a freight cartruck.
 5. An article made of steel according to claim 2 by casting.